EPILEPSY and OTHER SEIZURE DISORDERS 273 Base of Rh
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45077 Ropper: Adams and Victor’s Principles of Neurology, 8/E McGraw-Hill BATCH RIGHT top of rh CHAPTER 16 base of rh EPILEPSY AND OTHER cap height base of text SEIZURE DISORDERS In contemporary society, the frequency and importance of epilepsy logic disease that demands the employment of special diagnostic can hardly be overstated. From the epidemiologic studies of Hauser and therapeutic measures, as in the case of a brain tumor. and colleagues, one may extrapolate an incidence of approximately A more common and less grave circumstance is for a seizure 2 million individuals in the United States who are subject to epi- to be but one in an extensive series recurring over a long period of lepsy (i.e., chronically recurrent cerebral cortical seizures) and pre- time, with most of the attacks being more or less similar in type. dict about 44 new cases per 100,000 population occur each year. In this instance they may be the result of a burned-out lesion that These figures are exclusive of patients in whom convulsions com- originated in the past and remains as a scar. The original disease plicate febrile and other intercurrent illnesses or injuries. It has also may have passed unnoticed, or perhaps had occurred in utero, at been estimated that slightly less than 1 percent of persons in the birth, or in infancy, in parts of the brain inaccessible for exami- United States will have epilepsy by the age of 20 years (Hauser nation or too immature to manifest signs. It may have affected a and Annegers). Over two-thirds of all epileptic seizures begin in very small or “silent” area in a mature brain. The increasingly re- childhood (most in the first year of life), and this is the age period fined techniques of magnetic resonance imaging (MRI) are now when seizures assume the widest array of forms. The incidence beginning to reveal small zones of cortical dysplasia and hippo- increases again slightly after age 60. In the practice of pediatric campal sclerosis, both of which tend to be epileptogenic. Patients neurology, epilepsy is one of the most common disorders. The with such long-standing lesions probably make up the majority of chronicity of childhood forms and their persistence in patients of those with recurrent seizures but are necessarily classified as having all ages adds to their importance. For all these reasons, every phy- “idiopathic” or “cryptogenic epilepsy,” because it is often impos- sician should know something of the nature of seizure disorders sible to ascertain the nature of the original disease and the seizures and their treatment. It is, however, notable that in striking contrast may be the only sign of brain abnormality. to the many treatments available for epilepsy, as pointed out by There are other types of epilepsy for which no pathologic basis J. Engle, 80 to 90 percent of epileptics in the developing world has been established and for which there is no apparent underlying never receive treatment. cause except perhaps a genetic one. These epilepsies have been Epilepsy was in the past defined as an intermittent derange- referred to as primary. Included in this category are hereditary ment of the nervous system due to “an excessive and disorderly forms, such as certain generalized tonic-clonic (grand mal) and discharge of cerebral nervous tissue on muscles.” This was the “absence” seizure states. Some authors (Lennox and Lennox; For- postulate, in 1870, of Hughlings Jackson, the eminent British neu- ster) have reserved the term idiopathic for recurrent seizures of rologist, and modern electrophysiology offers no evidence to the these types. contrary. The discharge may result in an almost instantaneous loss of consciousness, alteration of perception or impairment of psy- CLASSIFICATION OF SEIZURES chic function, convulsive movements, disturbance of sensation, or some combination thereof. A terminologic difficulty arises Seizures have been classified in several ways: according to their from the diversity of the clinical manifestations. The term con- supposed etiology, i.e., idiopathic (primary) or symptomatic (sec- vulsion,referringasitdoestoanintenseparoxysmofinvoluntary ondary); their site of origin; their clinical form (generalized or fo- repetitive muscular contractions, is inappropriate for a disorder cal); their frequency (isolated, cyclic, or repetitive, or the closely that may consist only of an alteration of sensation or conscious- spaced sequence of status epilepticus); or their electrophysiologic ness. Seizure is preferable as a generic term, since it embraces a correlates. A distinction must be made between the classification diversity of paroxysmal events and also because it lends itself to of seizures (the clinical manifestations of epilepsy: grand mal, petit qualification. The term motor or convulsive seizure is therefore mal, myoclonic, partial, and others), considered below, and the not tautologic, and one may likewise speak of a sensory seizure classification of the epilepsies, or epileptic syndromes, which are or psychic seizure.Thewordepilepsy is derived from Greek disease constellations, most of which may manifest several seizure words meaning “to seize upon” or a “taking hold of.” Our pred- types. These are discussed later in the chapter. ecessors referred to it as the “falling sickness” or the “falling The classification to be followed here was first proposed by evil.” Although a useful medical term to denote recurrent sei- Gastaut in 1970 and was then refined repeatedly by the Commis- zures, the words epilepsy and epileptic still have unpleasant con- sion on Classification and Terminology of the International League notations to the laity and should be used advisedly in dealing with Against Epilepsy (1981). This classification, based mainly on the patients. clinical form of the seizure and its electroencephalographic (EEG) Viewed in its many clinical contexts, the first solitary seizure features, has been adopted worldwide and is generally referred to or brief outburst of seizures may occur during the course of many as the International Classification. A modified version of it is re- medical illnesses. It indicates that the cerebral cortex has been af- produced in Table 16-1. fected by disease, either primarily or secondarily. Convulsive sei- The strength of the International Classification lies in its easy zures by their nature, if repeated every few minutes, as in status applicability to patients with epilepsy and its universal adoption. epilepticus, may threaten life. Equally important, a seizure or a The main value of classifying a seizure by its clinical and EEG short series of seizures may be the manifestation of an ongoing neuro- features is the reasonable predictability of response to specific med- stand long 271 drop folio Copyright © 2005, 2001, 1997, 1993, 1989, 1985, 1981, 1977, by The McGraw-Hill Companies, Inc. Click here for terms of use. 45077 Ropper: Adams and Victor’s Principles of Neurology, 8/E McGraw-Hill BATCH LEFT top of rh 272 PART 2 CARDINAL MANIFESTATIONS OF NEUROLOGIC DISEASE base of rh cap height Table 16-1 ing frequency and severity of this group of disorders with age re- base of text International classification of epileptic seizures flects the accumulation of focal insults from trauma, strokes, and I. Generalized seizures (bilaterally symmetrical and without lo- other damage. cal onset) Partial or focal seizures are further classified as simple when A. Tonic, clonic, or tonic-clonic (grand mal) consciousness is undisturbed and complex when consciousness is B. Absence (petit mal) altered or impaired. Simple partial seizures are further classified 1. With loss of consciousness only according to their main clinical manifestations—motor, sensory, 2. Complex—with brief tonic, clonic, or automatic autonomic, or psychic. When one of these subjective manifesta- movements tions precedes the progression of the attack to a loss of conscious- C. Lennox-Gastaut syndrome ness, it is referred to as an aura and has commonly been regarded D. Juvenile myoclonic epilepsy as a premonitory sign or warning of the impending seizure. In re- E. Infantile spasms (West syndrome) ality, the aura represents the initial phase of a focal seizure; in some F. Atonic (astatic, akinetic) seizures (sometimes with myo- instances it may constitute the entire epileptic attack. clonic jerks) Generalized seizures are of two types—convulsive and non- II. Partial, or focal, seizures (seizures beginning locally) convulsive. The common convulsive type is the tonic-clonic (grand A. Simple (without loss of consciousness or alteration in mal) seizure. Less common is a purely tonic, purely clonic, or psychic function) clonic-tonic-clonic generalized seizure. The classic nonconvulsive 1. Motor–frontal lobe origin (tonic, clonic, tonic-clonic; generalized seizure is the brief lapse of consciousness or absence jacksonian; benign childhood epilepsy; epilepsia par- (petit mal); included also under this heading are minor motor phe- tialis continua) nomena such as brief myoclonic, atonic, or tonic seizures. 2. Somatosensory or special sensory (visual, auditory, ol- The classification of seizures and of the epilepsies is con- factory, gustatory, vertiginous) stantly being modified. In one of the latest versions, the so-called 3. Autonomic syndromic classification (Epilepsia 30:389, 1989), an attempt has 4. Pure psychic been made to incorporate all of the seizure types and epileptic syn- B. Complex (with impaired consciousness) dromes and to categorize them not only as partial and generalized 1. Beginning as simple partial seizures and progressing to but also according to their age of onset, their primary or secondary impairment of consciousness nature, the evidence of cortical loci of the epileptogenic lesions, 2. With impairment of consciousness at onset and the many clinical settings in which they occur. This classifi- III. Special epileptic syndromes cation is semantically difficult and, in our view, too complicated A. Myoclonus and myoclonic seizures as yet for general clinical application. Since many epileptic syn- B. Reflex epilepsy dromes share overlapping features, it is often not possible to fit a C. Acquired aphasia with convulsive disorder newly diagnosed case of epilepsy into a specific category in this D.